using System; 
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Data.Linq;
 
namespace System.Data.Linq.SqlClient {
 
    // converts correlated scalar subqueries into outer-applies 
    // must be run after flattener.
    internal class SqlRewriteScalarSubqueries { 
        Visitor visitor;

        internal SqlRewriteScalarSubqueries(SqlFactory sqlFactory) {
            this.visitor = new Visitor(sqlFactory); 
        }
 
        internal SqlNode Rewrite(SqlNode node) { 
            return this.visitor.Visit(node);
        } 

        class Visitor : SqlVisitor {
            SqlFactory sql;
            SqlSelect currentSelect; 
            SqlAggregateChecker aggregateChecker;
 
            internal Visitor(SqlFactory sqlFactory) { 
                this.sql = sqlFactory;
                this.aggregateChecker = new SqlAggregateChecker(); 
            }

            internal override SqlExpression VisitScalarSubSelect(SqlSubSelect ss) {
                SqlSelect innerSelect = this.VisitSelect(ss.Select); 
                if (!this.aggregateChecker.HasAggregates(innerSelect)) {
                    innerSelect.Top = this.sql.ValueFromObject(1, ss.SourceExpression); 
                } 
                innerSelect.OrderingType = SqlOrderingType.Blocked;
                SqlAlias alias = new SqlAlias(innerSelect); 
                this.currentSelect.From = new SqlJoin(SqlJoinType.OuterApply, this.currentSelect.From, alias, null, ss.SourceExpression);
                return new SqlColumnRef(innerSelect.Row.Columns[0]);
            }
 
            internal override SqlSelect VisitSelect(SqlSelect select) {
                SqlSelect save = this.currentSelect; 
                try { 
                    this.currentSelect = select;
                    return base.VisitSelect(select); 
                }
                finally {
                    this.currentSelect = save;
                } 
            }
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.